Your London extension, priced properly.
A builder-grade specification, an itemised fixed-price quote and three NAS Construction site teams — from a five-minute brief.
Local coverage
We know your street, not just your postcode.
Every one of 368 London neighbourhoods has its own page: local build rates, housing-stock quirks, planning temperament, party wall reality and access logistics.
Browse all London areasHow it works
From “I want an extension” to a shortlist — in minutes.
Tell us about your home
A short 7-step wizard covers your property, extension goals and finish.
See a realistic estimate
Based on London-specific per-sqm benchmarks and projects similar to yours.
Meet NAS Construction crews
Get matched with up to 3 NAS Construction specialists — no auctions, no spam.
The output
Not a ballpark. A builder's specification.
Finish the five-minute brief and you get a printable, contract-ready document — the same format a serious London contractor would issue on letterhead.
Elemental schedule A–J
Preliminaries, groundworks, superstructure, roof, MEP, finishes and fees — each with quantities, rates and amounts.
Contract sum + VAT
Provisional and PC sums flagged, contingency stated, VAT calculated — the number you sign is the number you pay.
Stage payment schedule
Six milestone releases tied to signed-off site triggers, convertible straight into invoices.
London cost guide
Real ranges, not guesswork.
London extensions typically run £3,000–£5,000 per sqm for architect-led, mid-spec projects. Our estimator layers your type, size, finish and features on top of borough-level benchmarks.
Get my personalised estimate| Extension type | Typical size | London range |
|---|---|---|
| Side return | 15–20 m² | £65k – £95k |
| Rear extension | 20–30 m² | £85k – £130k |
| Wraparound | 30–45 m² | £120k – £185k |
| Double-storey rear | 40–60 m² | £165k – £260k+ |
Shell + fit-out; excludes land, party wall and unusual site constraints.
Recent projects
London extensions we've scoped.
What homeowners say
Built on trust, not lead auctions.
“The estimate matched what our builder actually quoted. Saved us weeks of guesswork.”
“Being matched with three properly NAS Construction crews — instead of ten random ones — was the difference.”
“Loved how simple the form was. Felt like it was built for London specifically.”
Ready to see your numbers?
Answer 7 short questions to get your London-specific estimate and a shortlist of NAS Construction crews.